Tutorials – THz Science, Technology and Applications

Tutorial Title:

THz Science, Technology and Applications

Chair:

Wojciech Knap (IHPP-PAS Warsaw and L2C University of Montpellier and CNRS)

Abstract:

The tutorial session aims to address the subjects related to development of new THz detectors, amplifiers and sources in view of their application to passive and active imaging, security screening as well as to wireless communication systems. It is expected to demonstrate how new physical phenomena, new advances in materials technology as well as innovative devices design may lead to development of new high performance THZ systems. Special accent will be put to THz properties of Graphene and graphene-like topological phases of semiconductor heterostructures of III-V or II-VI materials- like HgCdTe or quantum wells for example. Independently the tutorial has as an objective to make review of recent developments of THz components and systems based on traditional semiconductor technology. The questions of the choice of the best semiconductor technology for THz imaging and wireless communications will be addressed. The speakers will be invited to present the problems of THz technology market and the problem of so called “killer” application. Particular attention will be devoted to the realization of sensors for focal plane arrays for real-time imaging. The feasibility of the THz active and passive vision systems will discussed.

Summarizing the objectives of this Symposium are to review the current state of the art in THz components and systems in USA, Asia and Europe, to provide a clear view on the current technologies and the required advances in material science and devices to achieve more efficient systems.

This tutorial will address the counter-intuitive physics of the ballistic transport in short channel semiconductor devices. It will focus on the plasma waves, which are the oscillations of the electron (or hole) density in a transistor channel. The equations describing the plasma oscillations are the hydrodynamic equations and the phenomena linked to the wave excitation and propagation in liquids all have their counterparts in the electronic or hole two-dimensional fluid. The nonlinearity of the electron transport leads to the rectification, frequency multiplication, or emission of the plasma waves with the commensurate detection or emission of sub-terahertz (sub-THz) or THz radiation. Transistors, heterostructures, nanostructure arrays, and metamaterials made of Si, GaAs, InGaAs, GaN, graphene, carbon nanotubes, and diamond all compete for the THz plasmonic applications. I will discuss the Dyakonov-Shur and “plasmonic boom” mechanisms of the plasmonic instabilities in the electronic fluid and will describe the emerging novel device designs, such as using “plasmonic stubs” to control the boundary and interface conditions. I will explain how the new regimes of the device operation, unique for the plasmonic transistors, enable the THz spectroscopy and interferometry. I will also present a new compact THz Field Effect Transistor model (implemented in SPICE and ADS). This model agrees well with the experimental data and is suitable for the design, parameter extraction, and characterization of the plasmonic transistors and circuits.

Bio:

Dr. Michael Shur is Roberts Professor at RPI and co-founder of Sensor Electronics Technology, Inc., and of Electronics of the Future, Inc. He has over 400 patents or patent applications and is Life Fellow of IEEE APS, ECS, and SPIE and Fellow of the National Academy of Inventors and of several other professional societies. His awards include IEEE Ebers, Kirchmayer, Donald Fink, and Sensors Council Awards, Tibbetts Award for Technology Commercialization, St. Petersburg Technical University and University of Vilnius Honorary Doctorates, Gold Medal of Russian Education Ministry, van der Ziel Award, Senior Humboldt Research Award, RPI Research Awards, and several Best Paper Awards. He is an IEEE EDS and Sensors Council Distinguished Lecturer and Foreign Member of the Lithuanian Academy of Sciences.

The paper overviews experimental and theoretical studies of photogalvanic and photon drag effects induced in various in three-dimensional (3D) and 2D topological insulators (TI) by polarized terahertz (THz) radiation. Photocurrent spectroscopy has been proven to be an important tool to study low-dimensional semiconductors graphene. In last several years it has been demonstrated that photogalvanics, magneto-photogalvanics and photon drag effect can also be efficiently use for probing topological surface and edge states. It is shown that THz radiation results in dc electric current, which is sensitive to the radiation polarization and may have a component changing the sign by reversing the radiation helicity. Photogalvanic and photon drag effects are very general and have already been demonstrated for different topological systems, including Bi1-xSbxTe 3D TIs, HgTe-based 2D and 3D TIs, and Pb1-xSnxSe TIs with large value of x. Further tool to study TI states yield magneto-photogalvanic effects, particularly the cyclotron resonance assisted current observed in HgTe-based Dirac fermions systems.

Here we present the state-of-the-art of the field, including both recent advances and well-established results. Several physical mechanisms of photogalvanics in TI systems are described. We discuss the phenomenological and microscopic theory of these phenomena and present experimental achievements. We also show that nonlinear transport opens up new opportunities for probing of Dirac electrons as well as address prospective of future theoretical and experimental studies.

Bio:

Prof. Dr. Sergey Ganichev received the Diploma of Physics degree and the Ph.D. degree from the St. Petersburg Politechnical University, Russia in 1980 and 1984, respectively. In 1997 he obtained the Dr. habil. degree from the Ioffe Physicotechnical Institute, St. Petersburg, Russia and in 2002 from the University of Regensburg, Germany. From 1980 till 2005 Prof. Dr. Ganichev has been working at the Ioffe Institute, St. Petersburg, Russia. In 1992 he joined the Institute for Experimental und Applied Physics at the University of Regensburg, Germany, where he is currently working as a full professor. His research interests are terahertz science and technology, nonequilibrium and nonlinear effects in semiconductors, tunnelling and photoelectrical phenomena in semiconductors and semiconductor nanostructures, electron gas heating, Bloch oscillations, spin physics in semiconductors, physics of graphene and topological insulators, and ratchet phenomena.

This tutorial will present a survey on recent developments in the rapidly expanding field of integrated-circuit-based terahertz technologies. In addition to a standard approach in which active devices directly amplify THz frequencies, a large number of novel devices rely on nonlinear properties that manifest above the cut-off frequencies of transistors. These include multiplier-based THz sources, detectors, heterodyne and subharmonic mixers. For example, at low frequencies a field effect transistor-based rectifier rely on standard resistive mixing, however with rising frequency, charge-density waves (or plasma oscillations) in the channel start playing an increasingly important role and enable detection and mixing far beyond classical cut-off frequencies. An aspect whose significance cannot be overestimated is that efficient devices can be fabricated conveniently by Si CMOS foundry technologies. Examples of efficient implementation of THz detectors and detector arrays as well as THz sources for free-space coupling applications using standard integrated circuit fabrication techniques will be discussed.

Bio:

Dr Alvydas Lisauskas (male) – graduated from Physics Faculty of the Vilnius University and received PhD in 2001 at Royal Institute of Technology, Stockholm, Sweden. From 2002 till 2017 worked at Physikalisches Institut, Frankfurt University, Frankfurt am Main, Germany, since 2013 also in Vilnius University (since 2017 running the joint lab with CPST, Vilnius). Has extensive experience in techniques of THz generation, mixing and detection, including technologies for manufacturing relevant components. Published 109 papers that accumulated 1416 citations (h-index = 19). Won a competition for a team leader position in CENTERA WG3 and will be developing THz-related integrated circuits there.

The research and development in the frequency region of 0.1-1.5 THz is extremely significant for wide range of applications, In spite of the problems in technology and high prices for basic components (e.g. phase shifters, directional couplers, etc.) in the THz systems meet expanding interest of consumers. Dielectric rod waveguides (DRW) are the promising transmission lines, when low loss dielectric materials are used, and can be combined with semiconductor devices (oscillators, detectors, mixers, etc.) in the hybrid and/or monolithic integrated circuits. DRW offer a new opportunity for passive and active component performance, as it allows to decrease the insertion loss. Besides, DRWs have no cut-off frequency enabling broad band operation. In, the DRW antenna was proved to operate in the frequency band of 0.1-1.1 THz. The DRW is an open, i.e., not metal-shielded, waveguide system allowing to affect it with outside electro-magnetic fields including light. If one of the DRW walls is covered with a variable impedance layer, the propagation constant can be tuned. Existing materials with tunable electrical parameters are usually very lossy at upper millimeter-wave to THz frequencies. Thin layers of optically-controlled carbon nanotubes (CNTs) are proposed in this paper as a novel solution. The simplicity of the CNT deposition gives an opportunity to cover a large area, which is essentially important for e.g. for reflector surface coating, sensor matrices, etc. CNT compo-nents can be integrated with DRW antenna elements for THz beam steering applications.

Bio:

Dr Dmitri V. Lioubtchenko (male) – graduated from Moscow Institute of Physics and Technology and obtained PhD in 1997 at Institute of Radioengineering and Electronics, Russian Academy of Sciences, Moscow. Subsequently a postdoc at the University of Liverpool, UK. From 1999 worked at Helsinki University of Technology on the dielectric rod waveguides and passive and active devices for millimetre wave integrated circuits based on these waveguides. In 2013-2017 senior scientist at Aalto University School of Science and Technology and since 2016 a Visiting researcher at Royal Institute of Technology, Stockholm. Published 70 papers, accumulating 519 citations (h-index=10). Won a competition for a team leader position in CENTERA WG4 and will developing THz passive elements.

This talk will start with a brief introduction presenting different kinds of transistors that can be used for THz detection FETs ( si-CMOS, HEMTS, and HBTs). Physical mechanisms responsible for THz radiation rectification will be discussed. Maximum theoretical responsivity of these different transistors will be compared. The theoretical introduction will be followed with examples of experimental studies of single transistors as well as their arrays. The postal security scanner will be presented as the main example of the THz scanner security application. Special attention will be payed to polarization sensitive detection. We will show how measurement of the radiation polarization can bring additional information in the nondestructive testing of different fiber injected materials.

Bio:

Prof. dr Wojciech Knap obtained his master and PhD degrees from Faculty of Physics – Warsaw University Poland. His PhD concerned the Terahertz (Far infrared) properties of narrow gap semiconductors HgTe and InSb. After his PhD degree (1985) he obtained a permanent assistant professor position at University of Warsaw Solid State Physics Department . In 1987 he left to France and worked at University of Montpellier, Grenoble High Magnetic Field Laboratory, Toulouse Pulsed High Magnetic Field Laboratory. In 1992 he obtained a permanent position at French National Centre for Scientific Research – CNRS – Montpellier. He worked as associated professor at USA – Rensellear Polytechnic Institute and Tohoku University Japan. His main scientific interests and activities are concentrated around Fair Infrared-FIR (Terahertz – THz) properties of semiconductors and in particular in basic physics and applications of Terahertz Plasma excitations in nanotransistors. He is currently coordinating/animating an International Laboratory – LIA-TERAMIR composed with 9 groups from France, Poland and Russia and CENTERA – EU founded Laboratory of THZ science and technology in Warsaw.